So I was playing Battlespire and ran into a Vermai. The sounds it makes are actually still in Morrowind's sound files.

you can find them in "Morriwnd/data files/sound/cr/_OLD. The sounds are the TempB files. They're pretty generic but I think since we use the same design and we want things to be like Bethesda would have made it, that we should use those sounds so it feels like a Bethesda creature.

On a slightly off topic note, the TempC sounds were actually recycled in Tribunal for the goblins.